1. Field of the Invention
The invention relates to a thin-film transistor liquid-crystal display (TFT LCD) driver. More particularly, the invention relates to a thin-film transistor liquid-crystal display driver with smaller layout area and lower power consumption than the conventional display driver.
2. Description of Related Art
At present, thin-film transistor liquid-crystal displays are superior to other types of displays at least in regards to overall size and portability. Because thin-film transistor liquid-crystal displays are constructed with an array having a multitude of display units, a complicated display driver circuit is required for delivering the signals to each of the display units. Improvements to the conventional thin-film transistor liquid-crystal displays can be made by miniaturizing the complicated display driver circuit.
Referring to FIG. 1, a display driver circuit of a conventional thin-film transistor liquid-crystal display is shown. The conventional display driver circuit includes a controller 100, a shift register 120 and a sample and hold circuit 140. The shift register 120 and the sample and hold circuit 140 are controlled by the controller 100 and deliver video signal to a display panel 200.
To illustrate the complexity of the conventional display driver circuit, the specifications of a standard VGA display panel (640.times.480) are used. A VGA display panel needs 640 driving paths. Under this condition, the shift register 120 and the sample and hold circuit 140 must include 640 processing units to individually deliver the 640 output pixel signals to the display panel 200.
As shown in FIG. 1, the output of the sample and hold circuit 140 is delivered to the display panel 200 via operational amplifiers 151, 152, 153, etc. According to the illustration of a VGA display panel described above, the sample and hold circuit 140 has a total of 640 outputs each of which is amplified by a separate operational amplifier 151, 152, 153, etc. Therefore, the conventional VGA display driver requires a total of 640 operational amplifiers.
Because operational amplifiers take up a large amount of circuit space and consume a great deal of power, the conventional display driver is seriously affected by high power consumption and large circuit area. Because TFT LCD displays are used in portable, battery powered computers, the high power consumption of the conventional display driver has serious disadvantages in regards to battery life. Furthermore, this high power consumption does not meet the low power design requirements of a so called environmentally friendly "green computer".
Moreover, the shift register 120 and sample and hold circuit 140 requiring 640 processing units each with a large circuit structure are not in accord with the spirit of circuit miniaturization.
These problems are exacerbated when the array of the display panel 200 has a greater resolution than VGA because the required circuit layout area of the display driver circuit greatly expands and the power demands are further increased.